JPS60138624A - Controller having battery backed-up ram - Google Patents

Abstract

PURPOSE:To avoid a faulty output generated by the uncertain data in a RAM by checking the back-up voltage of the RAM when a main power supply is applied and producing a voltage reducing signal when the back-up voltage is lower than a prescribed level. CONSTITUTION:When a main power supply is applied, a control part 21 first drives a relay 25 for a fixed period of time to open a relay contact 26 and meanwhile checks the output of a voltage detecting circuit 23. In this case, the voltage applied to terminals (a) and (b) from a battery 1 and the circuit 23 produces a voltage reducing signal. Then the part 21 processes an error in response to the voltage reducing signal. For this purpose, the entire area of a RAM22, for example, is cleared to avoid the output of the wrong data or signals. While an original action is carried out when the circuit 23 produces no voltage reducing signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a control device having a battery-backed RAM, and more particularly to a control device that is fail-safe when the voltage of a RAM backup battery drops or is turned off.

(Background of the Invention) For example, in a power-saving lighting control device, each lighting is pattern-controlled based on lighting pattern data stored in a memory. Furthermore, in devices using a central processing unit (CPU) such as a microprocessor, control programs for the CPU and various data necessary for operation are stored in memory and read out and used as appropriate. Such memories include RAM (random access memory) and ROM (read only memory). While RAM allows data to be written and read freely,
When the power is turned off, the stored data will be destroyed (volatile). On the other hand, although the ROM retains its contents even when the power is turned off, it is difficult or impossible to write or rewrite data. Therefore, a RAM backed up by an auxiliary power source consisting of a battery is used as one that satisfies both the requirements for writing and rewriting data and for retaining data when the power is turned off.

By the way, such battery-backed RAM
If the battery drops below the specified voltage, or if the main power of the device is turned off while the battery or the connector between the battery and RAM is disconnected, the contents will be destroyed and the next time the main power is turned on, Because the contents become undefined, the lighting pattern in the lighting control device described above becomes chaotic, and in the equipment using the CPLJ described above, the program may run out of control and may not operate or perform abnormal operations. There was an inconvenience.

(Object of the invention) The object of the present invention is to solve the problems of the conventional type described above.
In a control device that has a battery-backed RAM, the idea is to check the RAM backup voltage at the same time as the device's main power is turned on, and to obtain a detection signal to prevent device malfunction when the voltage drops or is cut off. Based on this, the object is to provide a fail-safe function against RAM backup voltage failure.

(Structure of the Invention) In order to achieve the above object, the present invention includes a main power source, a battery, and an RA backed up by the battery when the main power source is turned off.
M, which generates a control output based on the data stored in the RAM when the main power is turned on; For example, it is characterized in that it is provided with a voltage detection circuit that generates a voltage drop signal.

(Explanation of Examples) Hereinafter, the present invention will be explained in detail using the drawings.

The accompanying drawing shows a block configuration of a control device according to an embodiment of the present invention. In the figure, 1 is a battery, which is connected to backup voltage input terminals a and b of a control device 2 by a connector (not shown).

The control device 2 includes a control section 21 composed of a CPU, etc., and an RA.
M22 and a voltage detection circuit 23, which is a feature of the present invention, are provided.

When the main power is turned on, the control unit 21 reads data, for example, lighting pattern data, from the RAM 22 to pattern-control each lighting device that is a load, and writes data into the RAM 22 based on input data from a keyboard (not shown) or the like.

The RAM 22 operates on the voltage supplied from the main power supply when the main power supply is on, and operates on the battery 1 when the main power supply is off.
Data written when the main power is turned on is retained by the backup voltage supplied from the main power supply.

The voltage detection circuit 23 includes a comparator 24, which compares the reference voltage obtained by dividing the main power supply with the voltage between the terminals a and b, that is, the backup voltage, and determines the l\rackup voltage. Generates a voltage drop signal when the voltage is lower than the reference voltage.

Next, the operation of this control device will be explained.

In this device, when the main power is turned on, the control unit 21
First, the relay 25 is driven for a certain period of time to close the relay contact 2.
6 is opened, and during this time, the output of the voltage detection circuit 23 is inspected. If the voltage applied from the battery 1 to the terminals a and b at this time is lower than the reference voltage, the voltage detection circuit 2
3 generates a voltage drop signal, the control unit 21 performs error processing in response to this voltage drop signal. As this error processing, for example, the entire area of the RAM 22 is cleared to prevent erroneous data or signals from being output. Further, when the voltage detection circuit 23 does not generate a voltage drop signal, the original operation, such as illumination pattern control, is performed.

In the above description, the relay contact 26 is opened for a certain period of time immediately after the main power is turned on, and then the voltage between terminals a and b is checked. 1 is floatingly charged via the diode 21 and the charging current limiting resistor 28, so if the main power supply is turned on, the main power supply voltage will be applied between the terminals a and b via the resistor 28. This is because the original backup voltage will not be tested.

(Effects of the Invention) According to the present invention, when the main power is turned on, the RAM is first
It is possible to determine whether RAM battery backup was performed normally by checking the backup voltage of In the event of failure, it is possible to prevent abnormal output from occurring due to the use of uncertain data in the RAM.

It should be noted that the present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications without departing from the spirit of the present invention. For example, in the above embodiment, a battery-backed RAM is used to store control data such as lighting patterns, but a CPU control program may also be stored therein. In this case, when a drop in backup voltage is detected, the CPU is reset and stops operating.
It is preferable to prevent abnormal output from occurring. Further, in the above description, the RAM backup battery is floating, but a non-rechargeable dry battery or the like may also be used. If you do not charge the battery in this way,
The relays 25, 26 mentioned above are unnecessary. Further, the relay contact 26 described above may be inserted in series with the diode 28, or a transfer contact may be used to connect the common contact to the terminal a, the normally closed contact to the resistor 28, and the normally closed contact to the voltage detection circuit 23. It may be connected to the detection voltage input terminal of

[Brief explanation of the drawing]

The accompanying drawing is a block diagram of a control device according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Battery, 2... Control device, 21... Control part, 22... RAM123... Voltage detection circuit, a, b... Backup voltage input terminal. Patent Applicant Toshiba Electric Materials Corporation Agent Patent Attorney Tatsuo Ito Attorney Patent Attorney Tetsuya Ito

Claims (1)

[Claims] 1. It has a main power source, a battery, and a RAM that is backed up by the battery when the main power source is turned off, and the RAM is backed up by the battery when the main power source is turned off.
A control device that generates a control output based on data stored in an AM is provided with a voltage detection circuit that inspects the backup voltage of the RAM when the main power is turned on and generates a voltage drop signal if the voltage is below a predetermined value. A control device characterized by: 2. The control device according to claim 1, wherein the RAM is all cleared when the voltage drop signal is generated. 3. It has a CPLI that operates using the data stored in the RAM as a program, and the voltage drop signal causes the CPLI to operate as a program.
The control device according to claim 1, characterized by a PU.